In site-specific cardiac pacing methods, such as cardiac resynchronization therapy (CRT), cathodal stimulation is generally desired. In some cases, an anodal capture threshold may be lower than the cathodal capture threshold. As a result, a clinician may think that capture of a particular heart chamber is occurring at the cathode electrode site when in fact the evoked response is initiated at the anode electrode site. This change in activation sequence from an expected activation sequence of the heart may result in less benefit from a delivered therapy than intended or possible. This compromised therapeutic benefit may go unrecognized since the clinician will typically not realize that anodal capture is occurring instead of cathodal capture.
In particular, as multi-polar coronary sinus leads become commercially available for pacing and sensing in the left ventricle, anodal capture in the left ventricle can become a more common occurrence when a bipolar pair of electrodes positioned along the left ventricle is selected for pacing in the left ventricle. In CRT, anodal stimulation in the LV will result in a different activation sequence of the LV than expected. Doctors will typically select a cathode positioned at a desired pacing site, such as the near the LV base, paired with an anode that results in the lowest capture threshold to conserve pacemaker battery energy. In some cases, the selected anode may cause anodal capture only or a combination of anodal and cathodal capture. If the anode is nearer the LV apex than the base, less desired apical pacing will occur, unknown to the clinician.